PIK3CA and gastric cancer: In our study, we developed a GC panel incorporating TCGA and ACRG classification: EBV ISH for EBV-positivity, MMR protein (MLH1, PMS2, MSH2, and MSH6) for MSI tumors, druggable RTKs (HER2, EGFR, MET), PI3K pathway component (PTEN), and p53 protein.